Extended reach drilling apparatus &amp; method

ABSTRACT

A method for drilling a well in a formation including inserting a thruster, a first conduit, and a drill bit into a wellbore lined with a previous casing and applying a force to the first conduit with the thruster so that the thruster grips onto the previous casing.

The present application claims the benefit of pending U.S. ProvisionalPatent Application Ser. No. 60/731,988 filed Oct. 27, 2005 the entiredisclosure of which is hereby incorporated by reference.

FIELD OF INVENTION The present invention relates to an apparatus andmethod for drilling an extended reach well in a formation. BACKGROUND

In the production of hydrocarbon fluid from an earth formation,wellbores are drilled to provide a conduit for hydrocarbon fluid to flowfrom a subterranean reservoir to a production facility at the surface.The ability to drill longer and deeper wells at inclined angles(referred to as extended reach drilling or ERD) is becoming increasinglyimportant to the oil and gas industry. An ERD well is generally definedas a well with a throw ratio of approximately 2:1 where the throw ratiois the ratio of horizontal depth to true vertical depth (TVD). Someextended reach wells (characterized as ultra ERD wells) may have throwratios as high as 6:1.

Traditionally wellbores are formed in two phases. In the first phase, adrill string (or drill pipe) with a drill bit attached to the lower endis rotated by a kelly or rotary table located at the surface. As thedrill bit creates a hole in the earth, drilling mud is circulatedthrough the annular space between the drill string and the wellbore wallto cool the bit and transport cuttings (rock chips from drilling) to thesurface. In the next phase, the drill string and bit are removed and thewellbore is lined with a string of steel pipe known as casing. Thecasing serves to stabilize the newly formed wellbore and facilitate theisolation of certain areas of the wellbore adjacent to the hydrocarbonbearing formations. Once the casing is cemented in the wellbore, asmaller bit is inserted through the casing and used to drill deeper intothe earth. This process is then repeated and numerous sections of casingare installed until the desired depth is reached. When the well iscomplete, the entire string of casing resembles an extended, invertedtelescope.

To reduce costs and drilling time, a process known as “drilling withcasing” is often employed. This process involves attaching the drill bitto the same string of tubulars that will be used to line the wellbore.Because the same string is used, both phases of the wellbore formationcan be completed in a single trip. However, the traditional nestedarrangement of casing in a well causes the available diameter for theproduction of hydrocarbon fluid to decrease with depth in a stepwisefashion. This becomes a technical and economic problem for deep wellswith many separate casings because drilling a small diameter deep holebecomes very challenging. To overcome this problem, the oil and gasindustry has begun to experiment with new drilling and casing techniquesthat involve radially expanding individual casing strings as they areinstalled in the well in order to maximize the available diameter. Onesuch technique is described in WO 2004/097168 A1, which is hereinincorporated by reference. This technique known as “expandable”technology, eliminates the aforementioned telescoping effect, and mayenable the drilling of a “monodiameter well,” a well in which everyjoint of casing used to line the wellbore has the same diameter.

Another recent development is the replacement of conventional drill pipewith “coiled tubing.” Whereas conventional drill pipe is assembled fromrelatively short rigid lengths of pipe, coiled tubing is a single strandof flexible pipe that is capable of handling a drilling assembly. Adownhole drilling motor is used to create the mechanical energynecessary to rotate the drill bit and a tractor device that grips ontothe interior of the wellbore maintains the proper amount of weight onbit and holds the reactive torque from the motor.

Even with these recent advancements in drilling technology, operatorsstill encounter challenges drilling and running completions in extendedreach wells. One major limitation is overcoming the friction incurred bythe drill string rotating and sliding on the casing or formation.Frictional losses can reduce the weight on bit so much that it isimpossible to drill with a reasonable penetration rate. Sufficientweight on bit is required to force the drill bit into the formation.Thus, the maximum drilling depth for an ERD well is often limited by theweight on bit, torque, or resistance of the drill string.

In addition to the frictional problem, disposal of cuttings and steeringalso limit drilling of ERD wells. Because ERD wells are so deep andlong, cleaning the cuttings from the drill out of the hole poses achallenge. The need to steer the drill bit through three dimensionalrock formations is also costly and time-consuming because the operatoris often required to trip out of the hole multiple times to replace orchange equipment.

US Pat. No. 6,467,557 B1 discloses a means to overcome the challengesassociated with extended reach drilling using a rotary long reachdrilling assembly. The tool described comprises an elongated conduitextending through a bore, a drill bit for being rotated to drill thebore, a 3D steering tool on the conduit for steering the bit, and atractor on the conduit for applying force to the bit. The tractorincludes a gripper which can assume a first position that engages aninner surface of the bore and limits movement of the gripper relative tothe inner surface. The gripper can also assume a second position thatpermits substantially free relative movement between the gripper and theinner surface of the bore. A propulsion assembly moves the tractor withrespect to the gripper while the gripper position is in the firstposition.

WO9909290 discloses an extended reach drilling system for drilling aborehole in an underground formation. The ERD system comprises a drillbit, a motor for driving the drill bit, a drill-pipe to surface, ahydraulic cylinder/piston arrangement for providing the required weighton bit, the drill-pipe being coupled to a selected one of the cylinderand the piston of said cylinder/piston arrangement by swivel meansallowing rotation of the drill pipe relative to one of the cylinder orthe piston, the drill bit being coupled to the other one of the cylinderand the piston, and locking means for locking said selected one of thecylinder and the piston against the borehole wall, the locking meansbeing operable between an engaged and a disengaged position.

WO9708418 discloses a method and apparatus for propelling a tool havinga body through a passage. The tool includes a gripper including at leasta gripper portion, which can assume a first position that engages aninner surface of the passage and limits relative movement of the gripperportion relative to the inner surface. The gripper portion can alsoassume a second position that permits substantially free relativemovement between the gripper portion and the inner surface of thepassage. The tool includes a propulsion assembly for selectivelycontinuously moving the body of the tool with respect to the gripperportion while the gripper portion is in the first position.

There are several opportunities for improving existing drilling systemsto overcome the challenges associated with extended reach wells. First,there is an opportunity to overcome the problems associated withfrictional losses and maintaining weight on bit. Known systems mayencounter difficulty achieving the penetration rate necessary to drillextended reach wells. Although tractors and other gripping devices applysome additional force to the drill bit, a tractor's grip on the innersurface of the bore may be insufficient to overcome the frictionallosses especially if a rotary system is used. In addition to the problemassociated with frictional loss, there is also an opportunity to addressthe telescoping problem posed by conventional casing methods. Generally,the ability to drill a deep well is limited by the available diameter inthe deepest segment of the nested casing. Maximizing the diameter ofthis segment of casing would enable the operator to drill deeperextended reach wells.

SUMMARY OF THE INVENTION

The present inventions include a method for drilling a well in aformation comprising inserting a thruster, a first conduit, and a drillbit into a wellbore lined with a previous casing and applying a force tothe first conduit with the thruster wherein the thruster grips onto theprevious casing.

The present inventions include an apparatus for drilling a well in aformation through a wellbore lined with a previous casing comprising adrilling assembly and a thruster connectable to the drilling assembly;wherein the thruster is capable of gripping onto the previous casing andproviding a force to the drilling assembly.

The present inventions include a method for drilling a well in aformation comprising providing a wellbore lined with a previous casing,inserting a first drilling assembly comprising a drill bit at a distalend, a first conduit connectable to the drill bit, and a thrusterconnectable to first conduit, gripping the previous casing with thethruster, and drilling a well.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is better understood by reading the followingdescription of non-limitative embodiments with reference to the attacheddrawings, wherein like parts of each of the figures are identified bythe same reference characters, and which are briefly described asfollows:

FIG. 1 illustrates a side view of an extended/ultra extended reachdrilling apparatus and method.

FIG. 2 illustrates a side view of another embodiment of the extendedreach drilling apparatus and method.

DETAILED DESCRIPTION

Referring to FIG. 1, wellbore 101 is shown extending through formation102 and is lined with previous casing 103. First conduit 104, drill bit105, and thruster 106 are shown being inserted into wellbore 101. Inthis embodiment, first conduit 104 is a section of drilling casing;however, other similar oilfield equipment (e.g. liner) could be used.Thruster 106 is shown in this embodiment as a tractor. Any substitutedevice capable of gripping or applying force could be used.

In operation, the drilling assembly (comprising first conduit 104, drillbit 105, and thruster 106) is inserted into wellbore 101. In theembodiment shown, drill pipe 107 is used to perform this function;however, other oilfield equipment (e.g. coiled tubing) may be usedinstead. After the drilling assembly is inserted, thruster 106 applies aforce to first conduit 104 causing drill bit 105 to drill a hole andextend wellbore 101. Thruster 106 provides the necessary weight on bitfor penetration by gripping onto previous casing 103. The torquerequired to rotate drill bit 105 may be transferred by first conduit104. Although it is shown as a liner in this embodiment, first conduit104 may also be drilling casing or other oilfield equipment. It is alsopossible to insert a drill pipe inside the liner to transmit the torqueto drill bit 105.

Once wellbore 101 is extended, first conduit 104 is removed from thedrilling assembly and hung against previous casing 103. First conduit104 is optionally secured in place by expansion, cementing, or any othermethod. Drill pipe 107 is then used to remove the drilling assembly. Anew drilling assembly is lowered into wellbore 101 comprising drill bit105, thruster 106, and second conduit (not shown). The steps are thenrepeated until the desired depth is reached.

Turning to FIG. 2, wellbore 201 is shown extending through formation 202and is lined with previous casing 203. Drilling assembly 204 is beinglowered into wellbore 201. Thruster 205 and liner 206 are also shownbeing lowered into wellbore 201. In the embodiment shown, coiled tubing207 is used to perform this function; however, other oilfield equipment(e.g. drill pipe) may be used instead of coiled tubing. Drillingassembly 204 comprises drill bit 208, drill motor 209, steeringmechanism 210, mud pump 211 to drive steering mechanism 210, andexpander 212. Additional components (not shown) such as directionalassemblies, bent housings, bent subs, measurement while drilling (MWD)instruments, and other downhole tools may also be attached to drillingassembly 204.

In operation, after drilling assembly 204 is inserted into wellbore 201,the torque required to drive drill bit 208 is provided by drill motor211. The torque is transferred via the liner or via drill pipe or coiledtubing inserted in the liner. Thruster 205 applies a force to liner 206causing drill bit 208 to drill a hole and extend wellbore 201 and holdsthe reactive torque from the drill motor. Thruster 205 provides thenecessary weight on bit for penetration by gripping onto previous casing203.

Once wellbore 201 is extended, drilling casing 206 is removed from thedrilling assembly and hung against previous casing 203. Drilling casing206 is then expanded using expander 212. Optionally drilling casing 206may be expanded against formation 202. Drilling casing 206 may also beexpanded to be the same diameter as previous casing 203; it may also beexpanded so that it has a smaller diameter. Preferably drilling casing206 is expanded so that its outer diameter is substantially equal to theinner diameter of previous casing 203. Expander 212 may be a pig, cone,rotary expansion device, cyclic expansion device or any other expansiondevice. After expansion, drilling casing 206 is then optionally cementedin place. A new drilling assembly is lowered into wellbore 201 the stepsare then repeated until the desired depth is reached. The subsequentdrilling casings may each be expanded so that the wellbore ismonodiameter.

Those of skill in the art will appreciate that many modifications andvariations are possible in terms of the disclosed embodiments,configurations, materials, and methods without departing from theirspirit and scope. Accordingly, the scope of the claims appendedhereafter and their functional equivalents should not be limited byparticular embodiments described and illustrated herein, as these aremerely exemplary in nature.

1. A method for drilling a well in a formation comprising: inserting athruster, a first conduit, and a drill bit into a wellbore lined with aprevious casing; and applying a force to the first conduit with thethruster wherein the thruster grips onto the previous casing.
 2. Themethod of claim 1 further comprising forming a hole in the formation;wherein the diameter of the hole is larger than the diameter of thefirst drilling casing.
 3. The method of claim 2 further comprising:hanging the first conduit against the previous casing; expanding atleast a portion of the first conduit into contact with an interiorsurface of the previous casing; securing the first conduit; and removingthe thruster and the drill bit from the wellbore.
 4. The method of claim3 further comprising: inserting the thruster, a second conduit, and thedrill bit into the wellbore through the first conduit; and applying aforce to the second first conduit with the thruster wherein the thrustergrips onto the first conduit.
 5. The method of claim 4 furthercomprising forming a hole in the formation; wherein the diameter of thehole is larger than the diameter of the second conduit.
 6. The method ofclaim 5 further comprising: hanging the second conduit against the firstconduit; expanding at least a portion of the second conduit into contactwith an interior surface of the first conduit; securing the secondconduit; and removing the thruster and the drill bit from the wellbore.7. The method of claim 6 wherein the expanding is performed by a toolselected from the group consisting of pigs, cones, rotary expansiondevices, and cyclic expansion devices.
 8. The method of claim 7 whereinthe securing is performed by cement.
 9. The method of claim 8 whereinthe first conduit is selected from the group consisting of drillingcasing, liner, coiled tubing, and coiled tubing inserted in liner. 10.The method of claim 9 wherein the inserting and removing are performedby coiled tubing.
 11. The method of claim 9 wherein the inserting andremoving are performed by drill pipe.
 12. The method of claim 9 whereinthe inserting and removing are performed by liner.
 13. An apparatus fordrilling a well in a formation through a wellbore lined with a previouscasing comprising a drilling assembly and a thruster connectable to thedrilling assembly; wherein the thruster is capable of gripping onto theprevious casing and providing a force to the drilling assembly.
 14. Theapparatus of claim 13 further comprising a conduit connecting thethruster to the drilling assembly.
 15. The apparatus of claim 14 whereinthe drilling assembly comprises: a drill bit, a mud pump; a motor; asteering assembly; and an expander means.
 16. The apparatus of claim 15wherein the conduit is selected from the group consisting of drillingcasing, liner, coiled tubing and coiled tubing inserted in liner. 17.The apparatus of claim 16 further comprising coiled tubing capable ofinserting the drilling assembly and the thruster into the wellbore. 18.The apparatus of claim 16 further comprising drill pipe capable ofinserting the drilling assembly and the thruster into the wellbore. 19.The apparatus of claim 16 further comprising liner capable of insertingthe drilling assembly and the thruster into the wellbore.
 20. A methodfor drilling a well in a formation comprising: providing a wellborelined with a previous casing; inserting a first drilling assemblycomprising a drill bit at a distal end, a first conduit connectable tothe drill bit, and a thruster connectable to first conduit; gripping theprevious casing with the thruster; and drilling a well.
 21. The methodof claim 20 further comprising: providing a force to the first conduitwith the thruster; and forming a hole with the drill bit.
 22. The methodof claim 21 further comprising: hanging the first conduit against thehole; and expanding the first conduit.
 23. The method of claim 22further comprising: inserting a second drilling assembly comprising thedrill bit at a distal end, a second conduit connectable to the drillbit, and a thruster connectable to second conduit; and gripping thefirst conduit with the thruster.
 24. The method of claim 23 furthercomprising: providing a force to the second conduit with the thruster;and forming a second hole with the drill bit.
 25. The method of claim 24further comprising: hanging the second conduit against the second hole;and expanding the second conduit.
 26. The method of claim 25 wherein thefirst conduit and the second conduit are expanded to substantially thesame diameter.
 27. The method of claim 25 wherein the second conduit isexpanded to a diameter smaller than the diameter of the first conduit.28. The method of claim 25 wherein the second conduit is expanded sothat an outer diameter of the second conduit is substantially equal toan inner diameter of the first conduit.
 29. The method of claim 26further comprising producing oil with the well.
 30. The method of claim27 further comprising producing oil with the well.
 31. The method ofclaim 28 further comprising producing oil with the well.